Hi guys, I have made a post in similar vein to this one, and had a couple comments. I agree that when possible, using managed associations and individual destinations for each side of the association is a best approach. However I'm running into issues with the "hierarchical values" approach you mention below. Maybe it's just my hibernate mappings, or maybe there's an issue. Note, I end up having to use this approach in some cases (destination references a base-class, and collection associations reside in sub-class instances).
In the example used here, whenever I modify a value of a child (User Scenario) or grandchild (Scenario), because the save is going through the parent (PlanPoint), the Hibernate Assembler assigns the collection as though it were a property of the parent. At this point when the commit occurs, I get a "org.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session" Check out my post. (http://tech.groups.yahoo.com/group/flexcoders/message/63308) I'd be interested to know if you get this working (hierarchical values), could you post up an example of the hibernate mappings? thanks, PW --- In flexcoders@yahoogroups.com, "Jeff Vroom" <[EMAIL PROTECTED]> wrote: > > This relates to your other question about the association tags in the > <metadata> section. There are two ways you can work with non-primitive > object properties using FDMS. You can either have them be "managed > associations" or you can treat them as "hierarchical values". If you > choose the former, you define a destination for each data type and > explicitly define the relationships using the <metadata> tags: > one-to-many, one-to-one, etc (FDMS only pays attention to the ...-to-one > or -to-many suffix as it only cares about whether the association is > single or multi-valued). In this approach, each destination deals with > the changes made to objects of that type. If you create a new child > object and add it to a property on the parent for example, it will send > the create event to the child destination and then send an update event > to the parent destination. These are both executed in the same > transaction so they will both get committed at the same time. > > > > When you use the hierarchical values approach, the entire object graph > underneath that property is treated as a single value. Any changes made > to any state under that property is treated as a change to the > property's value. FDMS reports the change to the parent object's > destination and only tells you that the property of the parent changed. > We do give you the complete old and new values though of the parent > object so you can walk down and compare them to figure out the details > of what changed. Whenever you use this approach, the entire object > graph gets shipped back and forth for each change so it gets inefficient > as the object graph gets bigger. > > > > In this particular case, it sounds like the managed association feature > would be the best approach. You can create new objects on either the > client or the server - whichever makes the most sense for your > application. Simply adding a new object to the property of another > managed object is enough to "create it" for the system. We'll detect > that it is a new object and log both the create and update operations as > part of the batch. When you issue the "commit" call, both are sent to > the server as part of the same batch. > > > > Jeff > > > > ________________________________ > > From: flexcoders@yahoogroups.com [mailto:[EMAIL PROTECTED] On > Behalf Of simonjpalmer > Sent: Sunday, January 28, 2007 12:56 PM > To: flexcoders@yahoogroups.com > Subject: [flexcoders] parent-child hierarchy of data using Flex, FDS and > Hibernate > > > > Hi, > > I have a 4 level hierarchy of data in my application with a > bi-directional one-to-many relationship between each level as follows: > > PlanPoint (parent) > -- UserScenario (child) > ---- Scenario (grandchild) > ------ Competitor (great grandchild) > > I have a hibernate back end running under JBoss and I am using FDS to > synchronise the changes from my Flex UI. My DB will be Oracle, but > for the time being I am just testing with a HSQLDB for convenience. > > I have managed to create a destination in FDS which will retrieve the > parent objects. The hibernate mapping docs specify the further > retrieval of the graph of objects attached to them. This all works > fine and performs reasonably well, although I have been unable to get > any meaningful lazy loading to work (a problem for another time). > > My problem comes in that the user will interact deeply with the graph > of objects during the client session. This includes adding, removing > and updating objects at all levels. > > What I can't seem to get right is the interaction in the Flex layer > which copes with this level of interaction. > > For instance if I want to add a new Competitor to a Scenario do I > (i) create all new objects on the client and then synchronise the > server, or > (ii) initiate creation of a new object on the server and then modify > it on the client? > > I seem to have problems in both directions and the same isue for > delete and to a certain extent modify. > > I only have a single FDS destination defined, so any alterations > appear to go through the PlanPoint Object at the root of the tree and > as a result much more data gets passed back and forth than I would like. > > > I'm not sure if I am just a little simplistic in my design and need > more sophistication in my relationship between the client and server, > or whether I just need a bit more code in my client to manage the > object state. > > Any guidance would be greatly appreciated as I'm beginning to swim in > circles. >
